Length-length, length-mass and a proposed standard mass equation for horse barbel Barbus tyberinus Bonaparte, 1839

Relative weight (Wr) is an index of condition computed as the comparison between the actual weight of a fish and a standard weight (Ws) that is the weight of an ideal fish at the same length that is in good condition. Data on length and weight of horse barbel Barbus tyberinus, an Italian endemic species, were collected throughout the entire distribution range of the species. Data were then used to develop a Ws equation for the species by means of the Empirical Percentile (EmP) method. The EmP Ws equation, calculated on total length (TL), resulted: log10 Ws = -4.9671+3.0216 log10 TL - 0.0095 (log10 TL)2 (TL range 80-480 mm). In addition, length-length and length weight equations were provided. The TL-W equation was calculated as: W = -4.861+2.940 log10 TL. The standard length (SL)-TL equation was TL = 1.149 SL+0.445 while the fork length (FL)- TL was TL= 1.050 FL+0.629. The results provided useful information for the biology of the species and underlined the value of relative weight as a tool to evaluate the condition of fish.